Overall Design

OVERVIEW:

Based on the chosen conceptual design, the team created a preliminary design. The machine was divided into subsystems. The subsystems consisted of the container-gripping mechanism, the lowering/raising mechanism, and the system that would loosen the closure. Based on the specifications and experiments that were initially performed, the team had to resolve the optimal design and components that would fit within each subsystem. Components were constrained by cost, suitability, what is commercially available, and if they fit within the preliminary project specifications (such as size or weight).

Possible methods for gripping the container included a vice grip design, robotic hand, and multiple-point contacts. The team decided that a robotic hand would be too complex for the scope of the project and therefore eliminated the idea. When modeled in SolidWorks, the vice grip design proved to be incapable of gripping the wide range of bottle diameters required for the application. Large size bottles were gripped easily; however, the smaller diameter bottles caused the v-shaped vice grips to overlap. This would require a design that compensated for the overlap, and doing so would provide an off-centered grip. For these reasons, the team chose to pursue multiple-point contacts for the base gripping mechanism.

Methods of lowering/raising the top mechanism that would be responsible for unscrewing the bottle closure included lead screw directly driven by a rotary motor, worm gear, rack and pinion, linear actuator, four-bar mechanism, and linear motor. Calculations were performed for the four-bar mechanism. Using a one-inch stroke linear solenoid, the four-bar mechanism would translate the one-inch displacement on one end of the bar to a distance of four and a half inches on the other end (the displacement that the top mechanism has to move in order reach various bottle heights). The four-bar mechanism would provide this necessary translation, however the 11 lbs of force required on the closure translated to approximately 55 lbs of force that the solenoid had to provide. The team could not find a viable solenoid to achieve the required force, the power requirement was beyond the typical household products, and the force that would be generated was an unsafe value. Due to this, the four-bar mechanism was not pursued. After considerable product research, the team determined that a linear actuator would perform the required function.

The system that would unscrew the closure did not have many options. The only logical choice was to utilize a rotary motor. Based on this, the team created a preliminary design that along with the specifications would be the guideline for sizing motors, bearings, couplings, determining overall dimensions, weight, cost, electrical design, and power requirements.

The container-gripping mechanism was designed to use four-point contacts. The contacts are moved back and forth by a shutter-type mechanism that is driven by rotary motor. Using torque feedback to sense when the grippers are in contact with an object, the rotary motor drives the gripper contacts to the container and back to the home position. The following pictures show the gripping mechanism.

AUTOMATED PILL BOTTER OPENER OPERATION PROCESS: